On Fri, May 13, 2022 at 6:54 PM Matthew Bobrowski <repnop@xxxxxxxxxx> wrote: > > On Fri, May 13, 2022 at 05:14:57PM +0300, Amir Goldstein wrote: > > On Fri, May 13, 2022 at 4:18 PM Matthew Bobrowski <repnop@xxxxxxxxxx> wrote: > > > > > > On Sat, May 07, 2022 at 07:03:13PM +0300, Amir Goldstein wrote: > > > > Sorry Matthew, I was looking at the code to give you pointers, but there were > > > > so many subtle details (as Jan has expected) that I could only communicate > > > > them with a patch. > > > > I tested that this patch does not break anything, but did not implement the > > > > UAPI changes, so the functionality that it adds is not tested - I leave that > > > > to you. > > > > > > No, that's totally fine. I had to familiarize myself with the > > > FS/FAN_RENAME implementation as I hadn't gone over that series. So > > > appreciate you whipping this together quickly as it would've taken a > > > fair bit of time. > > > > > > Before the UAPI related modifications, we need to first figure out how > > > we are to handle the CREATE/DELETE/MOVE cases. > > > > > > ... > > > > > > > My 0.02$ - while FAN_RENAME is a snowflake, this is not because > > > > of our design, this is because rename(2) is a snowflake vfs operation. > > > > The event information simply reflects the operation complexity and when > > > > looking at non-Linux filesystem event APIs, the event information for rename > > > > looks very similar to FAN_RENAME. In some cases (lustre IIRC) the protocol > > > > was enhanced at some point exactly as we did with FAN_RENAME to > > > > have all the info in one event vs. having to join two events. > > > > > > > > Hopefully, the attached patch simplifies the specialized implementation > > > > a little bit. > > > > > > > > But... (there is always a but when it comes to UAPI), > > > > When looking at my patch, one cannot help wondering - > > > > what about FAN_CREATE/FAN_DELETE/FAN_MOVE? > > > > If those can report child fid, why should they be treated differently > > > > than FAN_RENAME w.r.t marking the child inode? > > > > > > This is something that crossed my mind while looking over the patch > > > and is a very good thing to call-out indeed. I am of the opinion that > > > we shouldn't be placing FAN_RENAME in the special egg basket and also > > > consider how this is to operate for events > > > FAN_CREATE/FAN_DELETE/FAN_MOVE. > > > > > > > For example, when watching a non-dir for FAN_CREATE, it could > > > > be VERY helpful to get the dirfid+name of where the inode was > > > > hard linked. > > > > > > Oh right, here you're referring to this specific scenario: > > > > > > - FAN_CREATE mark exclusively placed on /dir1/old_file > > > - Create link(/dir1/old_file, /dir2/new_file) > > > - Expect to receive single event including two information records > > > FID(/dir1/old_file) + DFID_NAME(/dir2/new_file) > > > > > > Is that correct? > > > > Correct. > > Exactly the same event as you would get from watching dir2 with > > FAN_CREATE|FAN_EVENT_ON_CHILD in a group with flag > > FAN_REPORT_TARGET_FID. > > Right, that makes sense. For FAN_CREATE and FAN_DELETE (not entirely > sure about FAN_MOVE right now), FAN_MOVED_TO FAN_MOVED_FROM are not different than FAN_CREATE FAN_DELETE they carry exact same info > as you mentioned can we simply provide > the DFID_NAME of the non-directory indirect objects? From a UAPI > perspective, I think in terms of what's expected in such situation > would be clear. > I think there may be some confusion. We are not suggesting to change anything w.r.t the event info. FAN_REPORT_TARGET_FID already defines that those dirent events on non-dir with carry DFID_NAME and FID of non-dir child. The only difference in behavior is that we are going to allow, with group flag FAN_REPORT_TARGET_FID, to set the dirent events in mask of a non-dir child to receive the exact same events with same event info as received today for a watching parent. Thanks, Amir.
